1. Field of the Invention
The invention generally relates to a method and device of grinding, and particularly relates to a method and device for grinding fine particulates.
2. Related Art
Nano-scale science and technology is currently the newest technology being developed by advanced countries. The nano-scale science and technology mainly includes three aspects of nano-elements, nano materials and nano inspection and characterization. Nano-elements are objects whose dimensions are measured in the nanometer scale. Nano materials have many special properties that are applicable in many kinds of industry.
In view of the development and application of nano-scale dye particulates, the nano-dye particulates produce less diffraction and make the color extremely pure and brilliant. The nano-dye particulates are also characterized in water-resistance, lightfastness and climate-resistance so that they will expand great markets in printing, dyeing and inkjet-printing, and facilitate the developments of high-value and high-performance delicate printing, fabric dyeing and high-level inkjet-printing.
Common dye particulates are made from a wet-dispersing process. The raw material of dye is mechanically driven and collided with hard grinding medium, so that the dye particles are dispersed into micro-scale particulates. The dye material and the grinding medium are imported into a grinding mill and moisturized with a grinding liquid. Blades or other stirring mechanisms are used to stir the dye material and the grinding medium at a high speed so as to disperse and grind the dye material. The dye particulates ground to a certain extent are then separated from the grinding medium by a screening mechanism and carried by the grinding liquid to a powder collector. The grinding blade or stirring mechanism is easy to be worn by the high-speed collisions of the dye material and the grinding medium. As a result, the grinding blade or stirring mechanism has to be replaced occasionally. In order to obtain a better result, a mechanical grinding system has also to be precisely controlled with the grinding parameters, which makes the design, installation and control of the grinding machine very delicate and complicated.
There is also a problem of particulate separation in the conventional grinding method. A common grinding machine utilizes mechanical devices such as a gap or a screen to separate the particulates from the grinding medium. For example, in U.S. Pat. No. 5,620,147, a micro-scale filter screen is used for separation of the particulates from the grinding medium. However, since the grinding medium is also small and easy to block and wear the screen, the separation is not quite satisfied. In U.S. Pat. No. 5,346,145, a gap-type separator having a stator and a rotor is used. However, it still encounters the problem of wear of the components and block-up of the grinding medium. Above all, the mechanical screening devices are limited with their dimensions that cannot achieve separation of finer particulates.
The nano-scale dye particulates, for example, are difficult to be separated from the grinding medium since they are all tiny particulates that cannot be screened with conventional mechanical screening devices. The difficulty also retards the development of nano-scale particulates.
In order to solve the aforesaid problems, the object of the invention is to provide a particulate grinding method and device in which two different kinds of force fields are applied to drive the particulates and the grinding medium respectively. The particulates and the grinding medium are driven and moved in different flow directions so as to collide with each other, and the particulates are dispersed. The grinding medium is controlled by a force field to flow in a grinding area, while the particulates are controlled by another force field to pass through the grinding area and circulate in another flow route. Since the particulates and the grinding medium are driven by different force fields, they are naturally separated after the collision and dispersion.
A grinding method according to the invention includes the following steps. First, providing a first force field for driving grinding medium flow in a specific area that is defined as a grinding area. Then, providing and controlling a second force field for driving the particulates pass through the grinding area, collide with the grinding medium and circulate in a flow route so as to disperse the particulates efficiently and continuously. And finally, guiding the finished particulates flow out and be collected. The kinds of the first and second force fields are determined by characteristics of the grinding medium and the particulates. For example, when the grinding medium is magnetic, the first force field can be a magnetic field. The second force field has to be chosen from a different kind so as to prevent the particulates from mixing with the grinding medium. For example, when the first force field is a magnetic field, the second force field is chosen from hydrodynamic force, electromagnetic field, gravitational field or others.
A particulate grinding device according to the invention includes: a chamber, having a grinding area in which a grinding medium is driven and moved by a first force field; a first driving mechanism for generating the first force field; a particulate flow pipe, connected to an inlet and an outlet of the chamber for circulating the particulates, having a filling port and a output port; and a second driving mechanism for generating a second force field. Particulate material is filled into the flow pipe from the filling port, driven by the second force field to flow into the chamber from the inlet and to collide with the grinding medium at the grinding area. Then, the particulates are driven to leave the chamber through the outlet, flow into the flow pipe and further circulate for the next collision and dispersion. The finished fine particulates are controlled to flow out from the output port.